Of the handful of voice-transcription iPhone apps to search the Web or place a call, Vlingo's is the best. Speaking into the phone searches the Web using Google or Yahoo, dials contacts, finds a place on a map, and updates your status on Twitter and Facebook without ever touching a keyboard.
Vlingo lacks the terrific, but iPhone SDK-violating feature to raise the handset to your head to begin a search, but makes up for it by creating a voice recognition profile for your phone book and by letting you preview Twitter and Facebook text before it updates your status.
A built-in browser would really push this app over the top. The current setup sends you to the iPhone's Safari browser when you search online, which makes you responsible for restarting the app if you want to pursue subsequent searches.